Co-pending U.S. application Ser. No. 13/547,031 entitled System and Method for Acute Neuromodulation, filed Jul. 11, 2012; the “'031 application”, filed by an entity engaged in research with the owner of the present application, is attached at the Appendix and incorporated herein by reference. The '031 application describes a system which may be used for hemodynamic control in the acute hospital care setting, by transvascularly directing therapeutic stimulus to parasympathetic nerves and/or sympathetic cardiac nerves using electrodes positioned in the superior vena cava (SVC). In disclosed embodiments, delivery of the parasympathetic and sympathetic therapy decreases the patient's heart rate (through the delivery of therapy to the parasympathetic nerves) and elevates or maintains the blood pressure (through the delivery of therapy to the cardiac sympathetic nerves) of the patient in treatment of heart failure.
Co-pending US application Ser. No. 14/642,699 (the '699), filed Mar. 9, 2015 and U.S. Ser. No. 14/801,560 (the '560), filed Jul. 16, 2015, each incorporated by reference, describe transvascularly directing therapeutic stimulus to parasympathetic and/or sympathetic cardiac nerves using electrodes positioned in the SVC, right brachiocephalic vein, and/or left brachiocephalic vein and/or other sites. As with the system disclosed in the '031, the methods disclosed in these applications can decrease the patient's heart rate (through the delivery of therapy to the parasympathetic nerves) and elevate or maintain the blood pressure (through the delivery of therapy to the cardiac sympathetic nerves) of the patient in treatment of heart failure.
The '699 and '560 applications describe one form of catheter device that may be used to perform transvascular neuromodulation. In particular, these applications shows a support or electrode carrying member 10 of the type shown in FIG. 1A on the distal part of a catheter member 14. The electrode carrying member 10 includes a plurality of struts 12. One or more of the struts carries one or a plurality of electrodes 17. The electrode carrying member 10 is designed to bias such electrodes into contact with the vessel wall. The electrodes 17 may be carried by the struts 12 in a variety of ways. For example, the electrodes may be mounted to or formed onto a substrate 15 that is itself mounted onto a strut or a plurality of struts, or the struts might be flex circuits including the electrodes, or the electrodes might be formed or deposited directly onto the struts. The material forming the struts 12 may have a shape set or shape memory that aids in biasing the circumferentially-outward facing surfaces (and thus the electrodes) against the vessel wall. The struts 12 or substrates 15 might utilize materials or coatings that allow the electrodes' active surfaces (those intended to be placed against the vascular wall) to be exposed, but that insulate the remainder of each electrode's surface(s) against loss of stimulation energy into the blood pool. In some embodiments, the struts 12 or substrate may be formed of an insulative substrate such as a polymer (including silicone, polyurethanes, polyimide, and copolymers) or a plastic. The electrodes can be constructed onto the strut or substrate using a variety of manufacturing techniques, including subtractive manufacturing processes (such as mechanical removal by machining or laser cutting), additive processes (such as laser sintering, deposition processes, conductor overmolding), or combinations (such as printed circuit technology with additive plating). In some embodiments, the struts and electrodes may be flex circuit or printed circuit elements.
As shown in FIG. 1B and as discussed in the '699 and '560, one strut may carry a plurality of electrodes, and those electrodes may be arranged in various configurations having different electrode densities and patterns.
In transvascular neuromodulation, including that described in the '031 application, it is important that the electrodes be properly positioned relative to the target nerve(s) in order to capture the target nerve fibers, while avoiding collateral stimulation of non-target nerve fibers. Mapping procedures are typically performed at the time of electrode placement within the vasculature, and may be repeated during therapy, to identify and/or fine tune the optimal electrode location. Mapping can be manually controlled by the clinician or automatically controlled by the neuromodulation system. During mapping, different electrodes, combinations of electrodes, or arrays can be independently energized while the target response to the stimulus is monitored. For stimulation relating to cardiac or hemodynamic function, parameters such as heart rate, blood pressure, ventricular inotropy and/or cardiac output might be monitored. In some cases mapping includes additional steps of repositioning the electrode carrying member so as to allow additional electrode sites to be sampled. The mapping process is performed until the optimal electrode or combination of electrodes for the desired therapy array is identified.
This application describes various electrode arrangements or arrays that may be used on an electrode support or strut for transvascular neuromodulation. The present application also describes electrode support configurations that allow the longitudinal and/or circumferential electrode position to be adjusted within a blood vessel without requiring repositioning of the entire electrode support.
This application also describes various electrode designs that may be used for transvascular neuromodulation. The electrodes may be used on electrode supports or struts of the type shown in FIGS. 1A-1C, or on catheters or other types of supports. In certain embodiments, electrode designs allow or promote the washing of blood between the conductive electrode surface and the surrounding vascular wall, so as to minimize accumulation or formation of organic material on the electrode surface where it can act as an insulator and thus impair energy delivery. In other designs, the electrodes are shaped to promote even current density. This application also describes electrode supports having retention features engageable with the surrounding vascular wall so as to maintain the electrodes in a stable position for the duration of therapy.
In transvascular neuromodulation, including that described in the '031 application, it is important that the intravascular electrodes be properly positioned sufficiently close to the target nerve(s) outside the vessel so as to capture the target nerve fibers. The present application also describes electrode support configurations that distend the vascular wall so as to bring the intravascular electrodes into proximity with the target nerve structures outside the vessel.
The electrode systems, support configurations, electrodes etc disclosed herein may be used in chronically-implantable or acute neuromodulation systems for carrying out transvascular nerve stimulation.